1. Field of the Invention
The present invention relates in general to switches used to activate a starting motor of a vehicle.
2. Description of the Prior Art
Known starter magnet switches are structurally arranged in such a manner that moisture and dust laden air flows from outside of the switch all the way into the innermost cavities thereof which contain the switch contacts. There, dust and water tend to accumulate on the fixed and movable contacts and degrade the performance of the switch. In cold weather, the water on the contacts freezes to ice which can completely prevent electrical contact from being made.
One known switch arrangement is disclosed in the Open Technical Report of Nippondenso No. 21-039 (issued on Jan. 20, 1981). A hole is formed in a plunger boot of the switch so that a plunger chamber within a coil communicates with the inside of a starter housing through a gap between an inner surface of the coil and an outer surface of the plunger. Accordingly, air compressed within the plunger chamber as a result of movement of a plunger flows into the inside of the starter housing through the gap and the hole of the plunger boot. The distance between the inside of the starter housing and the plunger chamber is short, and especially the length of the hole of the plunger boot is very short. Accordingly, upon the plunger's return stroke, water that has entered the starter housing may enter the plunger chamber through the short gap. Since the contact chamber communicates with the plunger chamber, the volume of the plunger boot and the plunger chamber becomes small when the plunger returns. Water having entered the plunger chamber moves easily into the contact chamber. Similarly, dust can easily enter into the conduct chamber. Water in the contact chamber freezes in cold weather thereby preventing electrical connection between contacts and dust accumulating in the chamber tends to deteriorate performance.